LPR Camera Installation
LPR Camera Installation
In order to achieve the best license plate recognition quality, you need to properly install the camera. Correct camera installation will allow you to get a high quality image and provide the best license plate recognition results. When you install the camera, you need to consider aspects such as vertical and horizontal view angles of the camera, the size of the license plate in the frame, lighting and other factors. Next, we will describe the main points that you need to pay attention to when installing a camera for recognizing vehicle license plates.
Please note that all the parameters below are not limited, but are recommended for the best recognition, i.e. you can go beyond these parameters, but the recognition quality can drop significantly.
The width of the plate in the image received from the camera should not be less than 100 pixels.
The tilt angle of the license plate should be within +/-10 degrees in relation to the horizontal line of the image.
The vertical angle of view of the camera should be no more than 30 degrees in relation to the road surface.
The horizontal angle of view of the camera should be no more than 30 degrees in relation to the direction of movement of the vehicle.
The camera installer can use the Pythagorean Theorem to calculate the camera's mounting height and tilt, and calculate the optimal distance from the vehicle to ensure the best license plate recognition.
For a simpler calculation of the minimum distance (D) from the camera to the vehicle, you can use the formula:
D = 1.7 * H, where H is the height of the camera installation.
For example, if the camera is installed at a height of 3 meters, then the minimum distance at which license plates can be recognized will be approximately 5 meters.
The maximum distance from the camera to the vehicle will depend on the optics of the camera and the range of the IR illuminator (if used).
If you need to recognize license plates from more than one lane, then it is recommended to mount the camera above the road using a crossbar as shown in the following figure.
When choosing an installation location, keep in mind that direct sunlight can light up the image and make it overexposed.
Place the camera on hard surfaces or stable pillars, as heavy vehicles may cause camera vibration, resulting in a blurry image.
When recognizing license plates at night or in low light conditions, it is necessary to install an IR illuminator.
Examples of correct camera installation: